1. Field of the Invention
The subject of the present invention is a process for the manufacture of suspensions containing finely divided basic aluminium halide, which produce good sweat reduction on human skin and are also simple to utilise.
2. Description of the Related Art
The prior art already includes a series of processes for the synthesis of aluminium hydroxyhalide complexes that can be used as antiperspirant active ingredients. Although the patents usually encompass the entire range of halides and other monovalent non-coordinating anions, only the chlorides have acquired a practical significance.
Apart from the standard processes for the manufacture of the simple ca. 50% aqueous aluminium chlorohydrate solutions by dissolving Al metal in a hypostoichiometric quantity of hydrochloric acid, processes for the synthesis of so-called activated aluminium chlorohydrates also exist.
For the manufacture of activated aluminium chlorohydrates, Gosling et al. (U.S. Pat. No. 4,359,456) start with standard aluminium chlorohydrate solutions and, after dilution at temperatures in the range between 50xc2x0 and 140xc2x0 C., perform tempering. This tempering leads to a change in the polymer species distribution. The higher molecular proportions of the standard aluminium chlorohydrate are broken down in favour of smaller species, so that the solution no longer contains species of larger than 100 xc3x85. Analytical characterisation of the aluminium chlorohydrate complexes made in this way was carried out with the aid of size-exclusion chromatography. Using this method, the proportion of low molecular complexes, and therefore the activation level, can be followed.
It has been found that the aluminium chlorohydrate complexes were particularly effective as antiperspirants if they contained high proportions of Band III (relative retention time ca. 0.79).
A similar synthesis concept was pursued by Fitzgerald et al. (UK-2 048 229) by ageing 10-25% aluminium chlorohydrate solutions at 50xc2x0 C. to 80xc2x0 C. for between 8 hours and 3 weeks.
According to both alternative processes, the species distribution produced by the activation conditions is not stable in aqueous solution, so that only through protective drying can an effective antiperspirant active ingredient that is stable in storage be obtained. The patents describe spray drying as the preferred drying method.
In antiperspirant finished formulations, currently either sieve fractions of the spray-dried powder (e.g. aerosols) or fine powders obtained by dry milling (roll-ons or sticks) are used.
It has thus not been possible previously to produce a stable effective aluminium antiperspirant active ingredient in liquid form. The processing of powder-form active ingredients, however always presents great problems for the formulator. Furthermore, due to the low pH value of the (humid) powder, the health of workers involved with it is endangered.
There was therefore a need for better, more easily handled antiperspirant active ingredients, without sacrificing the greater effectiveness of previous powder products. Furthermore, it was not possible to fulfill all the formulation wishes of the cosmetics industry with the powder-form aluminium chlorohydrate complexes available. For instance, the manufacture of certain semisolid formulationsxe2x80x94so-called soft solidsxe2x80x94proved to be extremely difficult.
It was then unexpectedly discovered that particularly easily handled and simultaneously effective aluminium hydroxyhalide-containing antiperspirant active ingredient suspensions were obtained when the active ingredient fulfilling the following formula and conditions
Al(OH)(3xe2x88x92b)XbzH2O
where
b=0.4 to 3, particularly b=0.45 to 1.0
z less than 4
X=halogen, particularly chlorine
whereby the HPLC chromatogram of the active ingredient has a band III share of  greater than 30%, particularly  greater than 40%, and optionally a buffer substance, is mixed into a non-aqueous oil phase while excluding humidity, and subsequently ground at temperatures below 60xc2x0 C. to the required fineness with a grinding device.
As a result of the direct wet grinding of the spray product, the laborious and dust-generating powder sieving and dry grinding is dispensed with, and suspensions are obtained that are more stable than those that can be obtained by suspension of dry-ground powder.
These antiperspirant active ingredients are non-aqueous suspensions characterised in that the non-aqueous phase consists of a substantially non-polar non-water-miscible organic liquid of the substance groups alkanes, isoalkanes, monofunctional alcohols, polyfunctional alcohols, fatty acid esters of monobasic and dibasic carboxylic acids with monofunctional and polyfunctional alcohols, polyoxyethylenes, polyoxypropylenes, polyalkoxylate ethers of alcohols, cyclic silicones, open-chain silicones and combinations of these. In particular, the non-aqueous oil phase consists of silicone oil.
According to the invention, silicone oil components used are cyclic silicones, open-chain silicones or mixtures of these. They can be used as mixtures with other cosmetically acceptable oils.
The finely divided antiperspirant suspensions according to the invention can contain the amino acids glycine and/or alanine as buffer substances.
The process for the manufacture of finely divided antiperspirant suspensions is characterised in that an aluminium salt effective as an antiperspirant may possibly be mixed in the presence of the amino acid, preferably glycine, with exclusion of humidity in a non-aqueous oil phase and then ground. A ball mill is preferably used as the grinding device.
An aluminium salt that is used and is effective as an antiperspirant, is a basic aluminium halide of the following composition:
Al(OH)(3xe2x88x92b)XbzH2O
where
b=0.4 to 3, particularly b=0.45 to 1.0
z less than 4
X=halogen, especially chlorine
where the HPLC chromatogram of the active ingredient preferably has a band III proportion of  greater than 30%, and particularly  greater than 40%.
In the case of the variant containing one amino acid, a basic aluminium halide of the following composition is used as an aluminium salt effective as an antiperspirant:
Al(OH)(3xe2x88x92b)Xb (amino acid) zH2O
where
X=halogen, especially chlorine
b=0.4 to 3, particularly b=0.45 to 1.0
z less than 2
and the molar ratio of amino acid to aluminium is between 0 and 0.33.
The grinding of the antiperspirant suspension in the process according to the invention is characterised in that this procedure is carried out at temperatures below 60xc2x0 C., and particularly at below 40xc2x0 C. The antiperspirant suspensions are advantageously applied in non-aqueous formulations, e.g. in aerosols, sticks and so-called soft solids. The following examples serve to illustrate the invention: